1. Field of the Invention
The present invention relates to a fuel cell stack comprising fuel cells stacked together, and a box containing the fuel cells. Each of the fuel cells is formed by stacking an electrolyte electrode assembly and a separator. The electrolyte electrode assembly includes a pair of electrodes and an electrolyte interposed between the electrodes.
2. Description of the Related Art
For example, a solid polymer electrolyte fuel cell employs a membrane electrode assembly (electrolyte electrode assembly) which includes an anode, a cathode, and an electrolyte membrane interposed between the anode and the cathode. The electrolyte membrane is a polymer ion exchange membrane. The membrane electrode assembly is sandwiched between separators to form the fuel cell.
The fuel cell of this type is used in a vehicle application, for example. For this purpose, in general, several tens to hundreds of fuel cells are stacked together, and the stack of the fuel cells is placed in a box to form a fuel cell stack. However, when an impact (external load) in a direction intersecting the stacking direction of the fuel cells is applied to the fuel cell stack, lateral displacement may occur in the fuel cells undesirably.
In an attempt to address the problem, for example, a fuel cell as disclosed in Japanese Laid-Open Patent Publication No. 2005-056814 is known. According to the disclosure, a unit cell is formed by sandwiching an MEA (membrane electrode assembly) between separators. A plurality of the unit cells are adhered together using adhesive to form a multi-cell assembly. The multi-cell assembly and a module frame form a multi-cell module. Terminals, insulators, and end plates are provided at opposite ends in a direction of stacking the multi-cell modules. In this state, a casing (outer member) is provided around the multi-cell modules such that outer binding members are provided between the multi-cell modules and the casing. Further, the casing is fixed by bolts and nuts to form a fuel cell stack.
However, in the conventional technique, the module frames holding the multi-cell assemblies each formed by adhering the unit cells together using the adhesive, the outer binding members receiving the module frames, and the casing receiving the outer binding members are provided, and such structure is significantly complicated.
Further, the performance of assembling the fuel cell stack is low, and the air and water cannot be discharged from the fuel cell stack smoothly. Moreover, the outer size of the fuel cell stack is large, and the volume and weight of the fuel cell stack are large.